The present invention relates to a combustion engine and, more particularly, to an airflow control system for an internal combustion engine having series turbochargers.
An internal combustion engine may include one or more turbochargers for compressing a fluid, which is supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chambers. The fluid compressed by the compressor may be in the form of combustion air or an air/fuel mixture.
An internal combustion engine having series turbochargers may include a wastegate valve between the exhaust manifold and the turbine section. As disclosed in U.S. Pat. No. 5,974,801 (issued to Houtz on Nov. 2, 1999), the wastegate valve may be actuated by compressed air from the intake manifold of the engine or an independent compressed air source. When actuated, the wastegate valve may bypass exhaust gas around the turbines.
Since compressed air from the high pressure compressor of series turbochargers is at high pressure and temperature, the wastegate valve must be made of materials capable of withstanding the high pressure and temperature. Such materials can greatly increase the cost of wastegate valve. However, using an independent compressed air source to provide compressed air to the wastegate requires the undesirable costs of an additional compressor and the energy to compress the air.
The present invention is directed to overcoming one or more of the problems as set forth above.
According to one exemplary aspect of the invention, an airflow system for an internal combustion engine having an intake manifold and an exhaust manifold is provided. The airflow system may include a first turbocharger including a first turbine coupled with a first compressor. The first turbine may be configured to receive exhaust flow from the exhaust manifold, and the first compressor may be configured to supply compressed air to the intake manifold. A second turbocharger may include a second turbine coupled with a second compressor, wherein the second compressor is configured to compress air drawn from atmosphere. The airflow system may also include a first conduit providing fluid communication between the first turbine and the second turbine, and a second conduit providing fluid communication between the second compressor and the first compressor. A wastegate valve is fluidly coupled with the exhaust manifold and movable between a first position and a second position. The first position allows fluid flow exhausted by the engine to bypass the first turbine, and the second position restricts fluid flow exhausted by the engine from bypassing the first turbine. The airflow system includes a third conduit providing fluid communication between the second compressor and the wastegate valve. The wastegate valve is moved to the open position at times when compressed air in the third conduit has at least a predetermined pressure.
According to another exemplary aspect of the invention, an internal combustion engine includes an intake manifold, an exhaust manifold, and an engine block. The engine block defines at least one cylinder being configured to receive compressed air via the intake manifold, and the exhaust manifold is configured to receive exhaust flow from the cylinder. The engine also includes a first turbocharger and a second turbocharger. The first turbocharger includes a first turbine coupled with a first compressor. The first turbine may be configured to receive exhaust flow from the exhaust manifold, and the first compressor may be configured to supply compressed air to the intake manifold. The second turbocharger may include a second turbine coupled with a second compressor, wherein the second compressor is configured to compress air drawn from atmosphere. The airflow system may also include a first conduit providing fluid communication between the first turbine and the second turbine, and a second conduit providing fluid communication between the second compressor and the first compressor. A wastegate valve is fluidly coupled with the exhaust manifold and movable between a first position and a second position. The first position allows fluid flow exhausted by the engine to bypass the first turbine, and the second position restricts fluid flow exhausted by the engine from bypassing the first turbine. The airflow system includes a third conduit providing fluid communication between the second compressor and the wastegate valve. The wastegate valve is moved to the open position while compressed air in the third conduit has at least a predetermined pressure.
According to yet another exemplary aspect of the invention, a method of controlling airflow to an internal combustion engine having an air intake manifold and an exhaust manifold is provided. The method may include imparting rotational movement to a first turbine and a first compressor of a first turbocharger with exhaust air flowing from the exhaust manifold of the engine. The method may also include imparting rotational movement to a second turbine and a second compressor of a second turbocharger with exhaust air flowing from an exhaust duct of the first turbocharger. The method may further include compressing air drawn from atmosphere with the second compressor and compressing air received from the second compressor with the first compressor. The method may also include supplying compressed air from the first compressor to the air intake manifold and supplying compressed air from the second compressor to a wastegate valve to control flow of the exhaust air from the exhaust manifold to the first turbine.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.